Use of airway pressure-based indices to detect high and low inspiratory effort during pressure support ventilation: a diagnostic accuracy study

Background Assessment of the patient’s respiratory effort is essential during assisted ventilation. We aimed to evaluate the accuracy of airway pressure (Paw)-based indices to detect potential injurious inspiratory effort during pressure support (PS) ventilation. Methods In this prospective diagnostic accuracy study conducted in four ICUs in two academic hospitals, 28 adult acute respiratory failure patients undergoing PS ventilation were enrolled. A downward PS titration was conducted from 20 cmH2O to 2 cmH2O at a 2 cmH2O interval. By performing an end-expiratory airway occlusion maneuver, the negative Paw generated during the first 100 ms (P0.1) and the maximal negative swing of Paw (∆Pocc) were measured. After an end-inspiratory airway occlusion, Paw reached a plateau, and the magnitude of change in plateau from peak Paw was measured as pressure muscle index (PMI). Esophageal pressure was monitored and inspiratory muscle pressure (Pmus) and Pmus–time product per minute (PTPmus/min) were used as the reference standard for the patient’s effort. High and low effort was defined as Pmus > 10 and < 5 cmH2O, or PTPmus/min > 200 and < 50 cmH2O s min−1, respectively. Results A total of 246 levels of PS were tested. The low inspiratory effort was diagnosed in 145 (59.0%) and 136 (55.3%) PS levels using respective Pmus and PTPmus/min criterion. The receiver operating characteristic area of the three Paw-based indices by the respective two criteria ranged from 0.87 to 0.95, and balanced sensitivity (0.83–0.96), specificity (0.74–0.88), and positive (0.80–0.91) and negative predictive values (0.78–0.94) were obtained. The high effort was diagnosed in 34 (13.8%) and 17 (6.9%) support levels using Pmus and PTPmus/min criterion, respectively. High receiver operating characteristic areas of the three Paw-based indices by the two criteria were found (0.93–0.95). A high sensitivity (0.80–1.00) and negative predictive value (0.97–1.00) were found with a low positive predictive value (0.23–0.64). Conclusions By performing simple airway occlusion maneuvers, the Paw-based indices could be reliably used to detect low inspiratory efforts. Non-invasive and easily accessible characteristics support their potential bedside use for avoiding over-assistance. More evaluation of their performance is required in cohorts with high effort. Supplementary Information The online version contains supplementary material available at 10.1186/s13613-023-01209-7.

. Comparison of parameters in different inspiratory effort groups using the criterion of inspiratory muscle pressure-time product o Table S2.Comparison of parameters in different inspiratory effort groups using the criterion of inspiratory muscle pressure o Table S3.Ten-fold cross-validation of airway pressure-based indices for diagnosis of high effort o Table S4.Ten-fold cross-validation of airway pressure-based indices for diagnosis of low effort o Table S5.Lower and upper limits of reference intervals of airway pressure-based indices classified by inspiratory muscle pressure per minute or inspiratory muscle pressure

o
Figure S1.Inspiratory muscle pressure, inspiratory muscle pressure-time product per minute, and airway pressure-based indices during downward pressure support titration o Table

Figure S1 .
Figure S1.Inspiratory muscle pressure, inspiratory muscle pressure-time product per minute, and airway pressure-based indices during downward pressure support titration

Table S1 .
Comparison of parameters in different inspiratory effort groups using the criterion of inspiratory muscle pressure-time product Data are shown as median (interquartile range) The low, intermediate, and high inspiratory effort was pre-defined as inspiratory muscle pressure-time product per minute of < 50, 50-200, and > 200 cmH2O•s•min -1 , respectively.∆Pes tidal swing of esophageal pressure, Pmus inspiratory muscle pressure, PTPmus inspiratory muscle pressure-time product, PEEPi intrinsic positive end-expiratory pressure, VTi inspiratory tidal volume, PBW ideal body weight, P0.1 airway occlusion pressure, ∆Pocc negative swing of airway pressure against end-expiratory airway occlusion, PMI pressure muscle index, VE minute ventilation a P < 0.05 pairwise comparison among the three groups b P < 0.05 low effort group compared to intermediate and high effort groups

Table S2 .
Comparison of parameters in different inspiratory effort groups using the criterion of inspiratory muscle pressure Data are shown as median (interquartile range)The low, intermediate, and high inspiratory effort was pre-defined as inspiratory muscle pressure of < 5, 5-10, and > 10 cmH2O, respectively.∆Pes tidal swing of esophageal pressure, Pmus inspiratory muscle pressure, PTPmus inspiratory muscle pressure-time product, PEEPi intrinsic positive end-expiratory pressure, VTi inspiratory tidal volume, PBW ideal body weight, P0.1 airway occlusion pressure, ∆Pocc negative swing of airway pressure against end-expiratory airway occlusion, PMI pressure muscle index, VE minute ventilation a

Table S3 .
Ten-fold cross-validation of airway pressure-based indices for diagnosis of high effort P0.1 the negative swing of airway pressure against end-expiratory airway occlusion at first 100ms, ∆Pocc the maximal negative swing of Paw against end-expiratory airway occlusion, PMI pressure muscle index, Pmus inspiratory muscle pressure, PTPmus inspiratory muscle pressure-time product, AUROC area under the receiver-operating-characteristics curve, PPV positive predictive value, NPV negative predictive value

Table S4 .
Ten-fold cross-validation of airway pressure-based indices for diagnosis of low effort P0.1 the negative swing of airway pressure against end-expiratory airway occlusion at first 100ms, ∆Pocc the maximal negative swing of Paw against end-expiratory airway occlusion, PMI pressure muscle index, Pmus inspiratory muscle pressure, PTPmus inspiratory muscle pressure-time product, AUROC area under the receiver-operating-characteristics curve, PPV positive predictive value, NPV negative predictive value

Table S5 .
Lower and upper limits of reference intervals of airway pressure-based indices classified by inspiratory muscle pressure per minute or inspiratory muscle pressure Pmus inspiratory muscle pressure, PTPmus inspiratory muscle pressure-time product, P0.1 airway occlusion pressure, ΔPocc negative swing of airway pressure against end-expiratory airway occlusion, PMI pressure muscle index